Hydrogel, especially those prepared using extracellular matrix, have been widely used in biomedicine field. Compared with the hydrogels prepared by synthetic material, the hydrogels prepared by extracellular matrix have many advantages, for example, being able to simulate the natural environment in organisms, high water content, good permeability, good biocompatibility and adjustable enzyme-degrading property etc (Silva et al., Curr Top Biol Dev, 64, 181, 2004; Drury et al., Biomaterials, 24, 4337, 2003). Even more important, extracellular substance matrix has biological induction effect, which can direct and induce the tissue-specific regeneration. For example, sodium hyaluronate is a natural extracellular matrix polymer, with biological functions such as management of cell adhesion and migration, regulation of cell division and differentiation etc. Sodium hyaluronate with high-molecular-weight can induce the bone marrow stem cells of chick embryo limbs to differentiate into cartilage cells (Kujawa et al., Develop Biol, 114, 519, 1986). Therefore the hydrogels prepared using extracellular matrix has been attracted more and more attention in biomedicine field (especially in tissue engineering field).
In many biomedicine applications, hydrogels are required to be in liquid state in the process of using, but to rapidly form gel after reaching the specified sites and lose their fluidity. Such rapid-gelating hydrogels have great advantages: suitable for any three-dimensional wound with complex shape; having a good adhesion to the wound; being used under endoscope and avoiding the open surgery and so on. So far, researchers have investigated a number of ways to realize the rapid-gelation of hydrogels. For example, water-soluble unsaturated derivatives of polyethylene glycol can be used to prepare gel through photo-initiated crosslinking; the tri-block copolymer solution (Pluronic poloxamer) with a specific composition of polyethylene glycol and polypropylene glycol has gelating behavior induced by temperature change (Leach et al., Am J Obstet Gynecol 162, 1317, 1990); cyanoacrylate can be crosslinked into gel through polymerization and used for tissue gluing; and glutaraldehyde-crosslinked materials of gelatin and so on. Generally speaking, the above hydrogels have various defects, such as poor biocompatibility, poor biodegradability and so on. Rapid-gelating usually needs the crosslinking agents with high activity, but these compounds usually have greater toxicity.
Thiol, a functional group naturally occurring in the biological body, has a good biocompatibility. It has high reactivity which is several orders of magnitude higher than amino group under the same conditions. Therefore, in order to provide rapid chemical cross-linking necessary for rapid-gelation, crosslinkers with high activity (e.g. formaldehyde etc) are needed to crosslink the relatively inert amino group, but this kind of cross-linkers have greater toxicity, and may cause side effects such as tissue inflammation etc., whereas biocompatible crosslinkers with low activity can be used to crosslink thiol to prepare hydrogels with good biocompatibility. Wallace et al dissolved multi-arm (four-arm or twelve-arm) polyethylene glycol thiol derivatives (molecular weight 10,000) into 0.3 mol/L sodium phosphate/sodium carbonate buffer solution (pH=9.6), multi-arm (four-arm or twelve-arm) polyethylene glycol succimide activated derivatives (molecular weight 10,000) in 0.0005 mol/L sodium phosphate buffer solution (pH=6.0) the, and the biocompatibility of hydrogel prepared through the mixing of above two solutions was greatly improved than the hydrogel prepared by using corresponding polyethylene glycol amino derivatives (Wallace et al, U.S. Pat. No. 6,624,245).
Although the method disclosed by Wallace et al is a better way for preparing rapid-gelating hydrogels, there are still many disadvantages (Wallace et al., U.S. Pat. No. 6,624,245). Firstly, N-hydroxyl-succinimide by-products are generated through the chemical crosslinking reaction between multi-arm polyethylene glycol thiol derivatives and multi-arm polyethylene glycol succimide activated derivatives, and they have certain toxicity. Secondly, multi-arm polyethylene glycol succimide activated derivatives and multi-arm polyethylene glycol thiol derivatives solutions adopted by Wallace et al are both unstable, and they need to be freshly prepared. Furthermore, the former solution should be used out within 1 h and the latter is prone to lose activity when contacting with the air and it is difficult to use. Thirdly, both multi-arm polyethylene glycol thiol derivatives and multi-arm polyethylene glycol succimide activated derivatives are very expensive, and only the concentration of the two compounds reaches to as high as 10% w/v or more (usually 20% w/v), respectively, rapid-gelating can be realized, and it is costly.
Invention Content:
One of technical problem to be solved in this invention is to provide a novel preparation method for biocompatible rapid-gelating hydrogel.
The other technical problem to be solved in this invention is to provide a novel preparation method for rapid-gelating hydrogel spray.
Part of terms defined in this invention is as follows:
The biocompatible thiolated macromolecule derivatives refer to the products of biocompatible macromolecules obtained through thiol modification. The mentioned biocompatible thiolated macromolecule derivatives contain at least 3 thiols, with molecular weight of 1,000˜10,000,000.
Biocompatible macromolecules refer to polysaccharides (chondroitin sulfate, heparin, heparan, alginic acid, hyaluronic acid, dermatan, dermatan sulfate, pectin, carboxymethyl cellulose, chitosan, etc.), their salt forms (e.g. sodium salt, potassium salt, etc.) and their chemical modified forms (e.g. carboxymethylation modification, hydrophobic modification, etc.), proteins (alkaline type gelatin, acidic type gelatin, alkaline type recombinant gelatin and acidic type recombinant gelatin, etc.) and their chemical modified forms (e.g. carboxylation modification and hydrophobic modification for amino group, etc.), and synthetic macromolecule (polyacrylic acid, polyaspartic acid, polytartaric acid, polyglutamic acid, and polyfumaric acid, etc.) and their salt forms (e.g. sodium salt, potassium salt, etc.) and their chemical modified forms (e.g. carboxymethylation modification, hydrophobic modification, etc.). The above chondroitin sulfate includes many types e.g. A type, B type and C type etc. The above biocompatible macromolecules do not include polyethylene glycol and its derivatives, as well as the oligomeric peptides containing cysteine, etc. (Lutolf et al, Biomacromolecules, 4, 713, 2003).
Thiol modification refers to a chemical reaction process for the introduction of free thiols, and usually includes the following chemical reaction processes: under the activation of carbodiimide, the side-chain carboxyl groups of biocompatible macromolecules react with diamine or dihydrazide containing disulfide bond to generate intermediate products, then disulfide bonds were reduced to give biocompatible thiolated macromolecule derivatives; or the mentioned biocompatible macromolecules' side-chain amino groups were directly modified to be thiol through chemical reaction.
Chemical cross-linking reaction refers to nucleophilic addition reaction and nucleophilic substitution reaction between thiols and thiol-reactive functional groups.
Hydrogel refers to a composite containing lots of water with a 3D crosslinking network structure, and the state between liquid and solid without fluidity. Gelation refers to the process through which the liquid state with fluidity turns into the hydrogel losing the fluidity, and gelating time refers to the time from liquid state with fluidity turns to the hydrogel losing the fluidity.
Alkylidene group refers to —(CH2)n— (n is an integer from 1˜15). Preferably n is an integer from 1˜8.
Substituted alkylidene group refers to the alkylidene group whose at least one hydrogen atom is substituted by alkyl, hydroxyl, amino, alkoxyl, phenyl, and ester group etc.
Aryl group refers to aromatic phenyl, naphthyl and so on, preferably phenyl.
Polyether group refers to —[(CHR)nO]m—, wherein R is alkyl, n is an integer from 1˜10, m is an integer from 1˜500. Preferably, R is hydrogen atom, n equals to 2, 3 and 4, respectively.
Alkyl refers to straight-chain or branched-chain alkyl with 1˜15 carbon atoms e.g. methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, sec-butyl, amyl, neoamyl, hexyl, heptyl, octyl and so on, preferably to straight-chain or branched-chain alkyl with 1˜10 carbon atoms, and preferably methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl and octyl.
Alkoxyl refers to straight-chain or branched-chain alkoxyl with 1˜6 carbon atoms e.g. methoxyl, ethoxyl, propoxyl, isopropoxyl, butoxyl, iso-butoxyl, tert-butoxyl, sec-butoxyl, pentyloxyl, neo-pentyloxyl, hexyloxyl, etc., preferably to straight-chain or branched-chain alkoxyl with 1˜4 carbon atoms, and preferably methoxyl and ethoxyl.
Ester group refers to —C(O)OR, wherein R is the above low-level alkyl, preferably carbomethoxyl, carbethoxyl, carbopropxyl and carbobutoxyl.
Carboxyl group refers to the carboxyl group (—COOH) and corresponding carboxylate (−COO−A+) after neutralized with alkali. The A+ includes sodium, potassium, lithium-ion, ammonia ion and so on, preferably carboxyl group, carboxylic sodium salt or carboxylic potassium salt.
The connecting group containing an amide bond refers to
in which R′ and R″ are the abovementioned alkylidene group, substituted alkylidene group, aromatic group or polyether group.
Polyamide group refers to the group generated by diacid and diamine.
One way to realize the preparation method for biocompatible rapid-gelating hydrogel in this invention includes the following steps:
(1) Component A and component B mix to form reactive mixture with specific crosslinking conditions, component A is a solution containing of biocompatible thiolated macromolecule derivatives, and component B is a biocompatible thiol-reactive crosslinking agent. Wherein, biocompatible thiolated macromolecule derivatives are prepared through thiolation of biocompatible macromolecules. The concentration of component A is less than 8% w/v, the pH value of component A is less than 8.5, and the pH value of component B is higher than that of component A. The thiols in component A reacts with the thiol-reactive functional groups in component B to give chemical cross-linking reaction, the sum of the concentration of biocompatible thiolated macromolecule derivative and the concentration of biocompatible thiolated-reactive cross-linking agent in mentioned reactive mixture is less than 6% w/v. The mentioned specific crosslinking conditions refer to the pH value of reactive mixture solution higher than 7.0.
(2) Reactive Mixture to Form Hydrogel
The basic chemical principle of preparation method for biocompatible hydrogel in this invention is the rapid chemical cross-linking reaction between thiols and biocompatible thiol-reactive functional group under the specific conditions. Generally, there are two active components in this invention: the solution of biocompatible thiolated macromolecule derivatives (component A) and biocompatible thiol-reactive crosslinking agent (component B). The biocompatible thiolated macromolecule derivatives containing at least 3 thiols in component A mix and chemically crosslink with the biocompatible thiol-reactive crosslinking agent containing at least 2 biocompatible thiol-reactive functional groups in component B under specific conditions, and thus this invention can be realized. This invention has the advantages of good biocompatibility, no by-products, good stability, easy to use, and low cost etc.
In this invention, component A refers to the solution containing thiolated biocompatible macromolecule derivatives. Water is the main solvent in the above solution, and also some salt component (e.g. sodium chloride, pH buffer salt component etc.) may be included to adjust osmotic pressure and stabilize solution pH, and also some polar and hydrosoluble components e.g. ethanol etc. may be included.
The biocompatible thiolated macromolecule derivatives used in this invention can be prepared through the thiol modification of biocompatible macromolecule, including direct thiol modification of the side-chain carboxyl group and amino group in biocompatible macromolecule. In addition, the side-chain hydroxyl group and amino group in biocompatible macromolecule can also be firstly conducted with carboxylation modifications to get new biocompatible macromolecule, and then the carboxyl group is thiolated. The thiol modification of biocompatible macromolecules generally includes the several following methods.
The method (I) is amino(hydrazide)/carbodiimide coupling chemical method for side-chain carboxyl group. The preferable way is that the carboxyl group forms intermediate product under the activation of carbodiimide, and then the diamine or dihydrazide containing disulfide bond conducts nucleophilic substitution and generates intermediate product, finally, the disulfide bond is reduced to thiol, and then the biocompatible thiolated macromolecule derivatives are obtained (Shu et al., Biomacromolecules, 3, 1304, 2002; Aeschlimann et al., U.S. Pat. No. 7,196,180 B1). The thiol-protected primary amine also can be used instead of the diamine or dihydrazide containing disulfide bond, and the biocompatible thiolated macromolecule derivatives can be formed after the thiol-deprotection of the obtained intermediate products (Gianolio et al., Bioconjugate Chemistry, 16, 1512, 2005). The above mentioned carbodiimide usually refers to 1-ethyl-3-(3-dimethylamine propyl) carbodiimide hydrochloride. Following is the structure of some amines or hydrazides containing disulfide bond:

Wherein, (1) is the Cystamine; (2) is the cystine ester; (3) is dithio diphenyl amine; (4) is dithio diethyl dihydrazide; (5) is dithio dipropyl dihydrazide; (6) is dithio dibutyl dihydrazide; (7) is dithio dipropionate diacyl glycine dihydrazide; (8) is dithio dipropionate diacyl alanine dihydrazide; (9) is dithio dipropionate diacyl(hydroxyl-) aminoacetate dihydrazide; (10) is dithio dipropionate diacyl aminopropylate dihydrazide; (11) is dithio dipropionate diacyl aminobutylate dihydrazide; (12) is dithio dibutanate diacyl glycine dihydrazide; (13) is dithio dibutanate diacyl aminopropylate dihydrazide; (14) is dimalonate diacyl cystamine dihydrazide; (15) is disuccinate diacyl cystamine dihydrazide; (16) is di(methyl) succinate diacyl cystamine dihydrazide; (17) is diglutarate diacyl cystamine dihydrazide; (18) is dihexanate diacyl cystamine dihydrazide; (19) is diheptanate diacyl cystamine dihydrazide.
The thiolated macromolecule derivatives prepared by this way generally have the following structures of general formula (I) or general formula (II) (Shu et al., Biomacromolecules, 3, 1304, 2002; Prestwich et al., WO2004/03716; Song et al., Application No. of China Patent of Invention: 200610119414.1).

Wherein R1 and R2 include alkylidene group, substituted alkylidene group, aromatic group, polyether group, amide group, polyamide and so on.
The method (II) is to prepare through the directly reaction of side-chain carboxyl group and carbodiimide containing disulfide bond (e.g. 2,2′-dithio-di(N-ethyl(N′-ethyl carbodiimide)) etc.), and the prepared biocompatible thiolated macromolecule derivatives have the following structure of general formula (III) (Bulpitt et al, U.S. Pat. No. 6,884,788).

Wherein R3 include alkylidene group, substituted alkylidene group, aromatic group and so on.
The method (III) is to modify side-chain amino group, the modification generally includes two methods (direct and indirect). Direct modification method refers to the direct modification of the side-chain amino group by introduction of thiol, e.g. the thiol modification of the amino group of collagen using disuccinate diacyl cystamine dicarbonyl-diimidazole activated ester (Yamauchi et al, Biomaterials, 22, 855, 2001; Nicolas et al, Biomaterials, 18, 807, 1997). The thiolated macromolecule derivatives prepared through direct modification method generally have the structure of general formula (IV) or the one similar to general formula (IV).

Wherein R4 includes alkylidene group, substituted alkylidene group, aromatic group, polyether group, amide group, polyamide and so on.
Indirect modification of amino group in method (III) generally includes two steps. The first step is carboxylation of amino group, and the second step is thiol modification of carboxyl group. Wherein, for the thiolation of carboxyl group in the second step is the same as the aforementioned method (I) and method (II). The thiolated macromolecule derivatives usually have the structure of general formula (V) or the one similar to general formula (VI).

Wherein the definition of R1 and R2 are the same with the aforementioned, and R5 includes alkylidene group and substituted alkylidene group etc.
For the biocompatible macromolecule contained both side-chain carboxyl and amino groups, its thiolated derivatives can simultaneously include carboxyl-thiolated structure (general formula (I) or general formula (II) etc.) and the structures by direct or indirect thiol modification of amino groups (general formula (III), (IV), (V) or (VI) etc.) (Song et al, Application No. of China Patent of Invention: 200710036276.5).
The method (IV) is the modification of side-chain hydroxyl. The common method is the carboxylation of hydroxyl under strong alkali condition, then the thiol modification of carboxyl according to the aforementioned method (I) and method (II). For example, the side-chain hydroxyl of macromolecules (cellulose, hyaluronic acid, chitin and chitosan etc.) can all be carboxymethylated, and then amino(hydrazide)/carbodiimide chemical reaction can be used in thiol modification. The prepared thiolated biocompatible macromolecule derivatives generally have the following structure of general formula (VII) or general formula (VIII).

Wherein the definition of R1 and R2 are the same as the aforementioned, and R6 includes alkylidene group and substituted alkylidene group etc.
The thiolated derivatives of the biocompatible macromolecule containing both side-chain carboxyl and hydroxyl group can simultaneously include carboxyl-thiolated structure (general formula (I) or general formula (II) etc.) and hydroxyl-thiolated structure (general formula (VII) or general formula (VIII) etc.)
In the above mentioned general formula (I)-(VIII), P refers to the residue of biocompatible macromolecule, wherein side-chain carboxyl, amino group or hydroxyl of biocompatible macromolecules are directly or indirectly modified to thiol, the molecular weight of P is 1,000˜10,000,000 in general, and the definition of biocompatible macromolecule is the same as the aforementioned.
In the above mentioned general formula (I)-(VIII), the preferred structures of R1 are alkylidene group —(CH2)m—, amide group
wherein m, i and j are all the integer of 1˜15. When m is the integer of 1˜3, i is the integer of 1˜5, when j is 2 and 3, it is just the specially preferred structure of R1.
In the above mentioned general formula (I)-(VIII), the preferred structures of R2 are aryl group, alkylidene group —(CH2)m—, and substituted alkylidene group
wherein m is the integer of 1˜15, R is methyl, ethyl, propyl and butyl. The specially preferred structures of R2 is the alkylidene groups whose carbon number is 2, R is the above mentioned substituted alkylidene group of methyl and ethyl.
In the abovementioned general formula (I)-(VIII), the preferred structures of R3 are aryl group and alkylidene group —(CH2)m—, wherein m is the integer of 1˜15, the specially preferred structure of R3 is the alkylidene group whose carbon number is 2.
In the abovementioned general formula (I)-(VIII), the preferred structures of R4 are alkylidene group —(CH2)m—, amide group
wherein m, i and j are all the integer of 1˜15. When m is the integer of 1˜3, i is the integer of 1˜5, when j is 2 and 3, it is just the specially preferred structure of R1.
In the above mentioned general formula (I)-(VIII), the preferred structures of R5 are alkylidene group —(CH2)m—, wherein m is the integer of 1˜15, when m is the integer of 1˜8, it is just the specially preferred structure of R5.
In the abovementioned general formula (I)-(VIII), the preferred structures of R6 is alkylidene group —(CH2)m—, wherein m is the integer of 1˜15, when m is the integer of 1˜5, it is just the specially preferred structure of R5.
The structures of part of preferred biocompatible thiolated macromolecule derivatives adopted in this invention are shown as follows:

Wherein structure formula (1), (2) and (3) belong to the specially preferred biocompatible thiolated macromolecule derivatives of general formula (I); structure formula (4) belongs to the specially preferred biocompatible thiolated macromolecule derivatives of general formula (II); structure formula (5) belongs to the specially preferred biocompatible thiolated macromolecule derivatives of general formula (III); structure formula (6) belongs to the specially preferred biocompatible thiolated macromolecule derivatives of general formula (IV); structure formula (7), (8) and (9) belong to the specially preferred biocompatible thiolated macromolecule derivatives of general formula (V); structure formula (10) belongs to the specially preferred biocompatible thiolated macromolecule derivatives of general formula (VI); structure formula (11), (12) and (13) belong to the specially preferred biocompatible thiolated macromolecule derivatives of general formula (VII); structure formula (14) belongs to the specially preferred thiolated biocompatible macromolecule derivatives of general formula (VIII).
For the biocompatible thiolated macromolecule derivatives synthesized by using the biocompatible macromolecule simultaneously having carboxyl, amino group and hydroxyl, their specially preferred structures may have one or more structures as structure formula (1)-(14). For example, hyaluronic acid simultaneously has carboxyl and hydroxyl, hydroxyl can be modified to carboxyl by carboxymethylating, then amino (hydrazide)/carbodiimide chemical reaction is conducted for thiol modification, the prepared thiolated hyaluronic acid derivatives simultaneously have the structure as shown in structure formula (1), (2) or (3) and structure formula (11), (12) or (13) (Prestwich et al., PCT Int. Appl. WO 2005/056608). Gelatin has both carboxyl and amino group, the amino can react with diacid anhydride to introduce carboxyl, then amino (hydrazide)/carbodiimide chemical reaction is conducted for thiol modification, the synthesized thiolated gelatin derivatives simultaneously have the structure as shown in structure formula (1), (2) or (3) and structure formula (7), (8) or (9) (Song et al., Application No. of China Patent of Invention: 200710036276.5).
The component B used in this invention is biocompatible thiol-reactive crosslinker which contains at least two thiol-reactive functional groups. In general, thiol-reactive functional groups usually contain maleimide, vinyl sulfone, α,β-unsaturated acrylate, α,β-unsaturated methacrylate, halogenated propionate, halogenated propionamide, dithio-pyridine and N-hydroxyl succinimide activated ester and so on. Wherein the functional groups e.g. maleimide, vinyl sulfone, iodo-propionate, iodo-propionamide, and dithio-pyridine etc. have higher thiol-reactivity. The reaction between above mentioned functional group and thiol can be divided into 3 types: (1) addition reaction between thiol and unsaturated double bond, wherein the functional groups belong to this reaction type including maleimide, vinyl sulfone, α,β-unsaturated acrylate, α,β-unsaturated methacrylate and so on; (2) substitution reaction of thiol, wherein the functional groups belong to this reaction type including iodo-propionate, bromo-propionate, chloro-propionate, iodo-propionamide, bromo-propionate, chloro-propionate, and dithio-pyridine etc. (3) thioesterification reaction, wherein the functional groups belong to this reaction type including the activated esters of all kinds of carboxylic acids e.g. N-hydroxyl succinimide activated ester and so on. The reaction equation between thiol and the above mentioned thiol-reactive functional groups are shown as follows:

In the above thiol-reactive functional group, N-hydroxyl succinimide activated ester has the stronger reactivity, and can react with both amino group and thiol without selectivity. Hence, it has considerable toxic and side effects. At the same time, a byproduct of N-hydroxyl-succinimide is generated when N-hydroxyl succinimide activated ester reacts with thiol, which may result in the producing of toxic and side effects. In addition, the thioester bonds formed between N-hydroxyl succinimide activated ester and thiol are not stable and apt to hydrolyse, which seriously restrict their application in medicine field. Although Wallace et al (U.S. Pat. No. 6,624,245) has ever used polyethylene glycol succimide activated ester derivatives to crosslink polyethylene glycol thiol derivatives, but because of the above serious disadvantages, this invention did not adopt N-hydroxyl succinimide activated ester as the thiol-reactive functional group. The reaction between dithio-pyridine and sulfhydryl also generates a byproduct, and it may also produce toxic and side effects, therefore, the present invention did not adopt either.
The thiol-reactive functional groups adopted by this invention including maleimide, vinyl sulfone, α,β-unsaturated acrylate, α,β-unsaturated methacrylate, α,β-unsaturated acrylamide, α,β-unsaturated methyl acrylamide, iodo-propionate, bromo-propionate, chloro-propionate, iodo-propionamide, bromo-propionate, and chloro-propionate etc. When iodo-propionate, bromo-propionate, chloro-propionate, iodo-propionamide, bromo-propionate, and chloro-propionate etc functional groups react with thiol, though byproduct are also generated, these byproducts are halogenated acids which can form chloride ion, bromide ion, or iodide ion under physiological condition, therefore, they also have good biocompatibility. Wherein halogenated propionate has better thiol-reactivity than corresponding halogenated propionamide, but its stability is worse; iodo-propionate (or iodo-propionamide) has better thiol-reactivity than corresponding bromo functional groups, but its stability is somewhat less; the thiol-reactivity of chloro-propionate (or chloro-propionamide) is the lowest, but its stability is better.
The preferred thiol-reactive functional groups in this invention are maleimide, vinyl sulfone, α,β-unsaturated acrylate, α,β-unsaturated methacrylate, α,β-unsaturated acrylamide, α,β-unsaturated methyl acrylamide, etc. These functional group not only have good biocompatibility, but also do not generate by-products when reacts with thiol. The specially preferred thiol-reactive functional groups in this invention are vinyl sulfone, α,β-unsaturated acrylate, α,β-unsaturated methacrylate, α,β-unsaturated acrylamide, and α,β-unsaturated methyl acrylamide, etc. They not only have good biocompatibility, but have greatly improved stability than N-hydroxyl succinimide activated ester.
The component B containing more than one thiol-reactive functional group adopted by this invention is usually the derivatives of polyethylene glycol (PEG) containing at least two aforementioned thiol-reactive functional groups e.g. two-arm, three-arm, four-arm, eight-arm or multi-arm PEG derivatives, and they have the following typical chemical structures:

Wherein F1, F2, F3, F4, F5, F6, F7 and F8 are the aforementioned thiol-reactive functional groups e.g. maleimide, vinyl sulfone, α,β-unsaturated acrylate, α,β-unsaturated methacrylate, α,β-unsaturated acrylamide, α,β-unsaturated methyl acrylamide, iodo-propionate, bromo-propionate, chloro-propionate, iodo-propionamide, bromo-propionate, and chloro-propionate etc., they can be the same, some of the same or totally different chemical structures. PEG refers to the chain segment with CH2CH2O repeated unit, and the molecular weight is from 100 to 1000000. Preferably, F1, F2, F3, F4, F5, F6, F7 and F8 are maleimide, vinyl sulfone, α,β-unsaturated acrylate, α,β-unsaturated methacrylate, α,β-unsaturated acrylamide, α,β-unsaturated methyl acrylamide etc functional groups, optimally, they are vinyl sulfone, α,β-unsaturated acrylate, α,β-unsaturated methacrylate, α,β-unsaturated acrylamide, α,β-unsaturated methyl acrylamide etc. functional groups.
Take two-arm PEG as an example, the common cross-linking agents was adopted by this invention including PEG dimaleimide, PEG divinyl sulfone, PEG di(methyl)acrylate, PEG di(methyl)acrylamide, PEG dihalogeno-propionate, and PEG dihalogeno-propionamide etc. The chemical structures are shown as follows:

The first step of one way to realize the preparation method for novel biocompatible rapid-gelating hydrogel in this invention is to prepare the reactive mixture solution with specific crosslinking conditions where the key point is to adjust the property of component A and component B to make the pH value of reactive mixture solution to be alkalescence or alkality. The preferable pH value of reaction mixture solution is 8.0˜12.0, especially preferably 8.5˜10.5.
As stated before, both the selected component A and component B in this invention have good biocompatibility, meanwhile, the chemical cross-linking reaction between thiol and thiol-reactive functional group also has good biocompatibility, which provides solid basis for good biocompatibility of this invention. In addition, to achieve rapid-gelation, other important parameters e.g. concentration of component A and component B, solution pH value, and temperature etc. should be optimized as well.
In this invention, the adopted temperature is generally 0˜50° C. The increase of the temperature of chemical crosslinking reaction can accelerate the gelating rate. During practical application, the preferred temperature is usually between 10˜40° C. The most common temperature in this invention is room temperature which is around 25° C.
In the preparation method for rapid-gelating hydrogel disclosed by Wallace et al, to realize rapid-gelating, the pH value of the used multi-arm PEG thiol derivative solution must be in stronger alkali condition (usually pH value is 9.6), and the solution's concentration must be more than 10% w/v (Wallace et al, U.S. Pat. No. 6,624,245). However, the thiol is unstable under alkalic condition, especially under stronger alkalic condition, and apt to form disulfide bond and then loses the reactivity. Therefore, the multi-arm PEG thiol derivative should be freshly prepared and is apt to lose reactivity when contacted with air, which is difficult to use. In this invention, for convenient use, the component A solution does not need to be prepared freshly, usually biocompatible thiolated macromolecule derivative is first used to prepare component A solution which can be stored under frozen at low-temperature after sterilization and be readily defrosted before use. Compared with the multi-arm PEG thiol derivative (molecular weight 10,000, at most 12 thiol/10,000 molecular weight chain segments) adopted by Wallace et al (Wallace et al, U.S. Pat. No. 6,624,245), the biocompatible thiolated macromolecule derivative adopted in this invention usually have greater molecular weight (usually between 10,000˜1,000,000) and higher thiol content (may be as much as 100 thiol/10,000 molecular weight chain segments) (Shu et al, Biomacromolecules, 3, 1304, 2002). Therefore, the component A in the invention is very unstable under stronger alkalic condition, and the disclosed method by Wallace et al can not be used to realize rapid-gelation (Wallace et al, U.S. Pat. No. 6,624,245).
In order to overcome the unstable defect of thiolated derivatives under stronger alkaline conditions, the pH value of component A adopted in this invention is usually below 8.5, preferably ≦7.0, at this time the solution has a certain stability. A more preferable pH range is 2.5˜7.0, under which the solution has good stability, and can be stored for more than one year at minus 30° C., it can be stored for more than 2 hours when the solution contacts the air at room temperature and stored for at least 5 hours without contact with the air at room temperature. The specially preferred pH range is 3.5˜6.0, under this condition the thiol are very stable, while the hydrolysis of biocompatible thiolated macromolecule derivatives by acids is mainly avoided. Under this specially preferred condition, the stability of component A adopted in this invention is essentially improved when compared with the multi-arm PEG thiol derivative solution adopted by Wallace, etc. (Wallace et al., U.S. Pat. No. 6,624,245) which is apt to be deactivated. It can be stored for more than 2 years at minus 30° C., even if contacting with the air at room temperature, it can be stored for more than 24 hours.
In this invention, the above mentioned conditions guarantee the long-term storage and good stability of component A before use. Also alkaline solution or alkaline substances can be added into the above component A before component A mixs with component B, to raise the pH value of component A (e.g. higher than 8.5), which is immediately mixed with component B to prepare hydrogel.
In this invention, the concentration of biocompatible thiolated macromolecule derivative in component A is usually less than 8.0% w/v, preferred concentration 0.5˜5.0% w/v, and especially preferred 0.8˜3.0% w/v. While in preparation method for rapid-gelating gel published by Wallace et al, in order to achieve rapid-gelating, the concentration of multi-arm PEG thiol derivative solution must be more than 10% w/v (usually 20% w/v) (Wallace et al., U.S. Pat. No. 6,624,245). When the concentration of component A is expecially preferred, the consumption of biocompatible thiolated macromolecule derivative in this invention is decreased by 80˜90%, which greatly reduces cost.
In this invention, the component A can be aqueous solution, in which sodium chloride, buffer salt and other ingredients can be added. Usually the buffer salt with a low concentration (e.g. 0.0005 mol/L weakly acidic sodium phosphate buffer solution) can stabilize the pH value of the solution, while sodium chloride etc. can adjust the osmotic pressure of the solution.
In this invention, the adopted biocompatible thiol-reactive cross-linking agents are very stable in solid state at low temperature, and usually it can be stored for a long term at minus 30° C. (more than two years); at the same time, they are readily to be dissolved, so the component B can be freshly prepared. The pH value of component B is higher than that of component A, and the pH value of component B is generally higher than 8.0, and usually ≧8.5, and its stable time at room temperature is generally more than 2 hours. For example, the polyethylene glycol diacrylate solution (pH 9.6) adopted in this invention can be stored at room temperature for 4 hours having no influence on the gelating time. In addition, under the same conditions, for polyethylene glycol dimethacrylate solution, polyethylene glycol diacrylamide solution and polyethylene glycol dimethyl acrylamide solution adopted in this invention, their stability are improved one by one, and furthermore they are all more stable than polyethylene glycol diacrylate solution. In this invention, the pH value of component B is preferred 8.0˜12.0, especially preferred 8.5˜10.5.
The component B adopted in this invention has great advantages. In the preparation method for rapid-gelating gel published by Wallace et al, the adopted cross-linker (multi-arm polyethylene glycol succimide activated derivatives) is very unstable at both acidic and alkaline conditions, and it must be dissolved into 0.0005 mol/L sodium phosphate buffer solution to get weakly acidic solution (pH 6.0). But even under this optimal condition, the solution stability is still very poor, it needs freshly prepared and must be used up within an hour.
In this invention, the concentration of biocompatible thiol-reactive cross-linking agent in component B is usually less than 10% w/v, preferred 0.5˜8.0% w/v, especially preferably 0.8˜4.0% w/v. In the methods disclosed by Wallace et al., in order to achieve rapid-gelating, the concentration of the adopted cross-linking agent (multi-arm polyethylene glycol succimide activated derivatives) solution must be more than 10% w/v (usually 20% w/v) (Wallace et al., U.S. Pat. No. 6,624,245). In this invention, when the especially preferred concentration of component B is used, the consumption of cross-linking agent is reduced by 60˜96%, which significantly reduces cost.
In this invention, component B usually uses alkaline buffer solution as the solvent, sodium chloride and other ingredients can also be added to adjust solution osmotic pressure. The concentration of the adopted buffer solution is generally higher, e.g. 0.3 mol/L sodium phosphate/sodium carbonate buffer solution (pH 9.0˜10.0) (adjust pH to preset value by adding 0.3 mol/L sodium dihydrogen phosphate solution into 0.3 Mol/L sodium carbonate solution), etc. Because the biocompatible cross-linking agent in component B usually does not change the solution acidity, the pH value of the buffer solution determines the pH value of component B solution.
When component A and component B are mixed, the reactive mixture with a special cross-linking condition is formed. At room temperature, the pH value of reactive mixture solution mainly determines the cross-linking and gelating speed, and the increase of pH value accelerates the cross-linking and gelating process. The pH value of the reactive mixture solution is usually higher than 7.0, preferably 8.0˜12.0, especially preferably 8.5˜10.5.
The pH value of reactive mixture is determined when component A mixed with component B, or may be regulated by adding acidic or alkaline solution. The pH value of reactive mixture solution is determined by the properties (e.g. solvent type, concentration and pH value of buffer solution etc.) of initial component A and component B. The solution of component A and component B may contain pH-buffering substance with different concentrations or without contain pH-buffering substance, and other polar and hydrophilic material can also be added. The adjustment of the properties of initial component A and component B solution can regulate the acidity or alkalinity of the reactive mixture to reach the specified pH value. For example, when component A is the aqueous solution of pH=6.0, the solvent of component B is 0.3 mol/L sodium phosphate/sodium carbonate buffer solution of pH=9.6, the reactive mixture solution of component A and component B is alkaline, and its pH value is usually 9.0˜9.6; the increase of the solvent pH value of component B can raise the pH value of reactive mixture solution, on the contrary, the pH value of reactive mixture may decrease.
In this invention, acid or base solution (e.g. 0.2 mol/L sodium hydroxide solution, etc.) with a certain concentration can also be added into the reactive mixture solution, or into the component A or component B solution before mixing, or into the reactive mixture solution during the mixing between component A and component B, to adjust the pH value of reactive mixture to the specified value, so as to realize appropriate gelating speed. However, this step is usually not required, and to adjust the properties of initial component A solution and component B solution can realize this invention.
In the invention, the amount of both biocompatible thiolated macromolecule derivatives and biocompatible thiol-reactive cross-linking agent used in this invention are relatively low, the sum of the two concentrations in reactive mixture is generally less than 6% w/v, usually 0.8˜3.0% w/v.
Selecting appropriate biocompatible thiolated macromolecule and biocompatible thiol-reactive cross-linking agent, regulating the solution property of component A and component B, and selectively adding acid/base to further regulate the pH value of reactive mixture solution, the gelating time can be regulated within several seconds to several minutes (even dozens of minutes) to suit for different medical applications. For example, this invention can be conveniently used for rapid-gelating hydrogel spray for treatment of postoperative complications of adhesion and realize the gelating time of less than 1 minute.
Another way to realize the preparation method for novel biocompatible rapid-gelating hydrogel by the invention includes the following 3 steps:
(1) component A and component B mix to form the reactive mixture of specific cross-linking condition, component A is a solution containing biocompatible thiolated macromolecule derivatives, component B is a biocompatible thiol-reactive cross-linking agent, component B is a solid or a solution, of which biocompatible thiolated macromolecule derivative is prepared by the thiol modification of biocompatible macromolecule, the concentration of component A is less than 8% w/v, the pH value of component A is less than 8.5, the thiol in component A and the thiol-reactive functional group in component B conduct chemical cross-linking reaction, and mentioned specified cross-linking condition refers to the pH value of reactive mixture solution ≦7.0;
(2) Adjust the pH value of reactive mixture solution to a specified alkaline range.
(3) The reactive mixture forms hydrogel.
The first step of this way is to prepare the reactive mixture solution with good stability, wherein the key is to control the pH value of the reactive mixture to be weakly acidic. In this way, its difference from the aforementioned method is that the biocompatible cross-linking agent (component B) can be in solid state, or in the form of solution having weakly alkaline, neutral or weakly acidic, and the pH value of the reactive mixture solution formed by mixing between component A and component B is ≦7.0, preferably 2.5˜6.0, now the reactive mixture solution has good stability, and can be stored for more than 1 hour in contact with air at room temperature. The especially preferred pH range is 3.5˜5.0, and the reactive mixture solution has good stability, and usually can be stored for more than 4 hour in contact with air at room temperature.
The second step of this way is to add alkali or alkaline buffer solution (e.g. 0.2 mol/L sodium hydroxide solution/potassium hydroxide solution, phosphate of pH=9.0˜12.0, carbonate buffer solution and so forth) into the reactive mixture solution with relatively good stability, and the pH value of the solution is adjusted to be weakly alkaline or alkaline, with the preferred pH value 8.0˜12.0, and especially preferred pH value 8.5˜10.5.
The third step of this way is that under the above mentioned condition, component A and component B in the reactive mixture solution rapidly form hydrogel. The adopted biocompatible thiolated macromolecule derivatives and biocompatible thiol-reactive cross-linking agent by this route are the same as those in the aforementioned route, and the other conditions of the route are the same as the foregoing route.
In this invention, to select appropriate biocompatible thiolated macromolecule and biocompatible thiol-reactive cross-linking agent, regulate the property of component A and component B, and regulate the pH value of reactive mixture solution to be specified value, the gelating time can be regulated within several seconds to several minutes (even dozens of minutes) to suit for different medical applications. For example, the invention can be conveniently used for rapid-gelating hydrogel spray for treatment of postoperative complications of adhesion and realize the gelating time of less than 1 minute.
The biocompatible thiolated macromolecule in component A adopted in this invention usually has high molecular weight and thiol content, its molecular weight is usually between 10,000˜1,000,000, and the thiol content can be as high as more than 100 thiol/10,000 molecular weight chain segments, that is, each biocompatible thiolated macromolecule with molecular weight 50,000 have 500 thiols. Compared with the disclosed polyethylene glycol thiol derivatives and cysteine-containing oligopeptides (Wallace et al., U.S. Pat. No. 6,624,245; Gravett et al., US2004/0225077A1; Qiu et al., Biomaterials, 24, 11, 2003; Hubbell et al., US2003/0220245A1, Lutolf et al., Biomacromolecules, 4, 713, 2003), the thiol content in biocompatible thiolated macromolecules adopted in this invention is increased more than 8 times at least, and the molecular weight has also been greatly increased. Therefore, under the same conditions, the ability of biocompatible thiolated macromolecules adopted in this invention to conduct chemical cross-linking to form gel has been greatly improved, and the performance (e.g. mechanical strength, stability, permeability, etc.) of the gel have also been greatly improved. In the above-mentioned reports involving polyethylene glycol thiol derivatives and cysteine oligopeptides etc., only very high concentration (usually more than 10% w/v) can realize rapid crosslinking gelation, moreover, their solutions are weakly alkaline or must be alkaline, their stability are poor, and they must be freshly prepared and can not contact with air; at the same time, the concentration of the adopted cross-linking agents is also very high (usually more than 10% w/v), the water content in prepared hydrogel is generally less than 90%, usually 80% or so. In contrast, in this invention, the rapid crosslinking gelation can be realized even in very small quantities of biocompatible thiolated macromolecule and biocompatible thiol-reactive cross-linking agent used in this invention, the Water content in prepared hydrogel is generally more than 94%, usually higher than 97%, and the hydrogel has better permeability and biocompatibility. In addition, the biocompatible thiolated macromolecules in component A adopted in this invention are usually prepared using extracellular matrix (e.g. hyaluronic acid, etc.), and they retain the extracellular matrix-specific biological functions e.g. promoting trauma healing, directing and inducing the specific regeneration of tissues etc.
The biocompatible thiolated macromolecule in component A adopted by this invention is very unstable under stronger alkaline condition, and the method disclosed by Wallace et al (Wallace et al., U.S. Pat. No. 6,624,245) cannot be used to realize rapid-gelating. For example, hyaluronic acid thiolated derivative is extremely apt to form disulfide bond under strong alkaline condition, and thereby lose activity (Shu et al., Biomacromolecules, 3, 1304, 2002). Generally speaking, if the pH value of component A in this invention is greater than 8.5, the solution is very unstable and very inconvenient for use, and loses the practical value. For this reason, the component A in this invention is usually stored under near-neutral or slightly acidic condition, to significantly improve long-term storage stability of component A and its stability during use. But on the other hand, the realization of rapid-gelating further depends on the higher pH value (relatively strong alkaline) of the reactive mixture. Therefore, in one of routes to realize this invention component B usually has relatively strong alkaline, the pH value of component B must be greater than that of component A, so that the reactive mixture of component A and component B can have higher pH value (relatively strong alkaline). At the same time, the biocompatible thiol-reactive cross-linking agent in component B adopted by this invention must have good stability under various conditions (including relatively strong alkaline). By regulating the solution property of component A and component B and selectively adding acid/base to further regulate the pH value of reactive mixture solution, this invention can be realized.
In another preparation route of this invention, the solution property of component A and component B can also be adjusted to let the reactive mixture of component A and component B under weakly acidic condition, which can not only improve long-term storage stability of component A as well as component B and their stability during use, but also significantly improve the stability of reactive mixture during use, and then alkali can be added to further adjust the pH value of reactive mixture to relatively strong alkaline, to realize rapid-gelation.
Currently, although there are a small number of reports disclosing the hyaluronic acid thiolated derivatives, chondroitin sulfate thiolated derivatives and gelatin thiolated derivatives crosslinked by polyethylene glycol diacrylate (or polyethylene glycol divinyl sulfoxide), the adopted methods are all the same i.e. dissolving polyethylene glycol diacrylate (or polyethylene glycol divinyl sulfoxide) and thiolated derivatives into buffer solution, respectively, and adjusting the pH value of the two solutions to be the same near-neutral (usually 7.4), and then mixing the two solutions to prepare hydrogel. In this approach, however, it's difficult to achieve rapid-gelation. To simultaneously increase the pH value of the two solutions (e.g. 8.5 above) can accelerate the gelating process, but now the thiolated derivative solution is unstable, it may lose activity after several hours (usually around 0.5˜4 hours), at room temperature even without exposure to the air, difficult for long-term storage, and it's also difficult for large-scale industrial production, and difficult to use. For example, Liu et al (Liu et al, Fertility & Sterility, 87, 940, 2007) reported the application of Carbylan-SX (polyethylene glycol diacrylate crosslinked hyaluronic acid thiolated derivatives) hydrogel spray in prevention and treatment of postoperative adhesion. The adopted approach is to dissolve polyethylene glycol diacrylate and hyaluronic acid thiolated derivatives into buffer solution, respectively, and adjust the pH value of the two solutions to 7.4, sterilize by filtration, then mix two solutions, the viscosity of the mixture solution may be gradually improved about 5 minutes later; now spray the solution to the surface of wound tissue by spraying device. However, this approach has many obvious defects, e.g. long gelating time and difficult to control gelating process as well as difficulty in selecting the time for spraying etc. Spraying can only be realized in a very narrow time range when the viscosity of mixed solution is very high and also the solution has not lost fluidity yet. When its viscosity is not high enough, the solution is apt to flow away from the surface of wound tissue; but when its viscosity is too high, the solution cannot be sprayed. Connors et al. also applied the same Carbylan-SX and its preparation method in prevention and treatment of postoperative pericardial adhesion (Connors et al., Surg Res, 140, 237, 2007), but the same above defects also exist.
In addition, this invention also provides a novel preparation method for biocompatible rapid-gelating hydrogel spray, which is a method for applying the aforementioned preparation method for biocompatible rapid-gelating hydrogel in this invention to spray form of biocompatible rapid-gelating hydrogel.
In this method, the various spraying equipment suitable for multi-component mixed reactions can be adopted. The more commonly used spraying equipments include Spray Set for TISSEEL Fibrin Sealant (Baxter AG, USA), FibriJet (Micromedics Inc. USA) and so on. FibriJet series include ordinary atomization applicator kit and gas assisted atomization applicator kit. The ordinary atomization applicator kit of FibriJet series is suitable for low viscosity solutions, and the applicator tips are easily blocked and it's difficult to use. The structural schematic diagram of gas assisted atomization equipments of FibriJet series is shown in FIG. 1, including syringes 2A and 2B, syringe plunger clip 1, syringe holder 3, four-way applicator tip 4 and a pressurized gas inlet tubing 5. Syringes 2A and 2B are used for loading two components, respectively, which are squeezed out through four-way applicator tip 4, respectively, for atomization and mixing (or atomization following extrusion and mixing), then the gel forms after the solution is sprayed on the object's surface (e.g. trauma surface). The spray tip can also be added to improve atomization effect by connecting with the four-way applicator tip 4.
The key component of gas assisted atomization applicator kit of FibriJet series is the four-way applicator 4 (as shown in FIG. 2). Two inlets connect with two syringes 2A and 2B, respectively, and used for loading two components, one inlet (pressurized gas inlet pipe 5) connects with pressure gases (air or other gases), two components are extruded at the outlet, respectively, atomized and mixed under the effect of pressurized gas, then the gel formed after the solution is sprayed on the object's surface. The higher the pressure of pressurized gas is, the better the atomization effect is, however, too high gas pressure may cause harm to the human body. Usually the adopted gas pressure range is 1˜10 atmospheric pressure. When the gas pressure is relatively low and approximate to one atmospheric pressure, the atomization is not enough and relatively large liquid particles are formed, and the mixing is not very homogeneous; when the gas pressure is increased to 1.7 atmospheric pressure or so, very small liquid can be formed by atomizing, and the mixing is very homogenous. Component A and component B in one route of preparation method for biocompatible rapid-gelating hydrogel in this invention can be filled into two syringes, respectively, to prepare rapid-gelating hydrogel spray. Meanwhile, the spraying can be realized by the other route regarding to the preparation method for biocompatible rapid-gelating hydrogel of this invention, wherein the reactive mixture formed by the mixing between component A and component B is filled into one syringe, while alkali or alkaline buffer solution is filled into the second syringe, then the two were extruded at the outlet, respectively, then atomized and mixed under the effect of pressurized gas, thus the rapid-gelating hydrogel spray is prepared.